Staminal Evolution In The Genus Salvia Lamiaceae Molecular Phylogenetic Evidence For Multiple Origins Of The Staminal Lever Jay B Walker Kenneth J Sytsma Dept of Botany University of Wisconsin Madison Annals of Botany in press Abstract Background and Aims The genus Salvia has traditionally included any member of the tribe Mentheae Lamiaceae with only two stamens and with each stamen expressing an elongate connective The recent demonstration of the non monophyly of the genus presents interesting implications for staminal evolution in the tribe Mentheae In the context of a molecular phylogeny we characterize the staminal morphology of the various lineages of Salvia and related genera and present an evolutionary interpretation of staminal variation within the tribe Mentheae Methods Two molecular analyses are presented in order to investigate phylogenetic relationships in the tribe Mentheae and the genus Salvia The first presents a tribal survey of the Mentheae and the second concentrates on Salvia and related genera Schematic sketches are presented for the staminal morphology of each major lineage of Salvia and related genera Key Results These analyses suggest an independent origin of the staminal elongate connective on at least three different occasions within the tribe Mentheae each time with a distinct morphology Each independent origin of the lever mechanism shows a similar progression of staminal change from slight elongation of the connective tissue separating two fertile thecae to abortion of the posterior thecae and fusion of adjacent posterior thecae We characterize a monophyletic lineage within the Mentheae consisting of the genera Lepechinia Melissa Salvia Dorystaechas Meriandra Zhumeria Perovskia and Rosmarinus Conclusions Based on these results we can demonstrate 1 the independent origin of the staminal lever mechanism on at least three different occasions in Salvia 2 Salvia is clearly polyphyletic with five other genera intercalated within Salvia and 3 staminal evolution has proceeded in different ways in each of the three lineages of Salvia but has resulted in remarkably similar staminal morphologies Key words staminal morphology Salvia Mentheae Dorystaechas Meriandra Perovskia Rosmarinus Zhumeria Lepechinia Melissa key innovation floral evolution Staminal evolution in Salvia p 2 The genus Salvia Lamiaceae tribe Mentheae represents a cosmopolitan assemblage of nearly 1000 species displaying a remarkable range of variation in growth form secondary compounds floral form and pollination biology Salvia has radiated extensively in three regions of the world Central and South America 500 spp Western Asia 200 spp and Eastern Asia 100 spp Each of these radiations displays the unusual morphological character which has led to the long standing assumption that Salvia is monophyletic the significant elongation of the connective tissue of the two expressed anthers Fig 2 The demonstration of the non monophyly of the genus Walker et al 2004 has led to a reinvestigation of the staminal morphology within Salvia and closely related genera in the Mentheae This paper presents a molecular phylogeny of Salvia and related genera characterizes the staminal morphology in the various lineages of the genus Salvia and closely related genera and interprets that staminal morphology in a phylogenetic context Salvia is distinguished from the other 72 genera in the tribe Mentheae by having the two posterior stamens aborted and the connective separating the thecae of the two expressed stamens significantly elongated Fig 2 It is the elongation of the staminal connective that enables the formation of the lever mechanism of pollination for which Salvia is best known Fig 1 see Cla en Bockhoff et al 2003 2004a for thorough reviews The significant species radiations that are correlated with the presence of the lever mechanism in Salvia suggest it is the lever mechanism in a selective regime of pollination that is driving evolution in the group Cla en Bockhoff et al 2004b The significance of this lever mechanism to the reproductive biology in Salvia first described by Sprengel 1793 has received considerable attention Muller 1873 Zalewska 1928 Hruby 1934 Werth 1956 Baikova 2002 2004 Cla en Bockhoff et al 2003 2004a Wester and Cla en Bockhoff 2005 Himmelbaur and Stibal 1932 1934 directly addressed staminal evolution in Salvia presenting a hypothesis of parallel evolution of the lever mechanism from a common ancestor in the New World and the Old World We present here the first robust Salvia wide molecular phylogeny with sampling across the tribe Mentheae to directly evaluate Himmelbaur and Stibal s 1932 1934 hypothesis Additionally the following questions are addressed and answered How many times has an elongate connective originated in Salvia and related genera How many times has the staminal lever mechanism originated in Mentheae What are the most closely related genera to Salvia What are the trends in staminal evolution within Salvia The results will support independent origins of the staminal lever mechanism on at least three different occasions From a common ancestor we document remarkably similar yet independent progressions in staminal evolution each presumably under pollinator selection and each arriving at strikingly similar functional endpoints in a staminal lever MATERIALS AND METHODS Taxa sampling Nomenclature for Salvia follows that suggested by Alziar 1988 1993 144 trnL F sequences 139 nuclear rDNA ITS sequences and 85 psbA trnH sequences representing Staminal evolution in Salvia p 3 38 genera and 144 species were obtained in this project Table 1 Accessions vouchers locality and GenBank numbers are available in Table 1 The data matrix for the Mentheae wide analysis combined ITS psbA trnH and trnL F and consisted of 84 taxa The data matrix for the Salvia clade analysis combined ITS and trnL F and consisted of 93 taxa Outgroups chosen for the Mentheae wide analysis were Ocimum basilicum and Hyptis alata both from the tribe Ocimeae Within the Mentheae 34 genera were sampled that represented every subtribe within the Mentheae Within the Salvia clade analysis sampling concentrated on the genus Salvia 82 species sampled and all genera indicated by the Mentheae wide analysis to be closely related to Salvia Horminum pyrenaicum was selected as the outgroup for the Salvia clade analysis based on the results of the Mentheae wide analysis Extractions amplification and sequencing Total genomic DNA was
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